Clinical, Diagnostic, and Management
Perspectives of Aortic Dissection*
Ijaz A. Khan, MD, FCCP; and Chandra K. Nair, MD, FCCP
The incidence of aortic dissection ranges from 5 to 30 cases per million people per year,
depending on the prevalence of risk factors in the study population. Although the disease is
uncommon, its outcome is frequently fatal, and many patients with aortic dissection die before
presentation to the hospital or prior to diagnosis. While pain is the most common symptom of
aortic dissection, more than one-third of patients may develop a myriad of symptoms secondary
to the involvement of the organ systems. Physical findings may be absent or, if present, could be
suggestive of a diverse range of other conditions. Keeping a high clinical index of suspicion is
mandatory for the accurate and rapid diagnosis of aortic dissection. CT scanning, MRI, and
transesophageal echocardiography are all fairly accurate modalities that are used to diagnose
aortic dissection, but each is fraught with certain limitations. The choice of the diagnostic
modality depends, to a great extent, on the availability and expertise at the given institution. The
management of aortic dissection has consisted of aggressive antihypertensive treatment, when
associated with systemic hypertension, and surgery. Recently, endovascular stent placement has
been used for the treatment of aortic dissection in select patient populations, but the experience
is limited. The technique could be an option for patients who are poor surgical candidates, or in
whom the risk of complications is gravely high, especially so in the patients with distal dissections.
The clinical, diagnostic, and management perspectives on aortic dissection and its variants, aortic
intramural hematoma and atherosclerotic aortic ulcer, are reviewed.
(CHEST 2002; 122:311–328)
Key words: acute aortic syndrome; aortic dissection; aortic intramural hematoma; atherosclerotic aortic ulcer; clinical
features; diagnosis; dissecting aneurysm; dissecting hematoma; prognosis; treatment
Abbreviations: dP/dt П­ first derivative of pressure; TEE П­ transesophageal echocardiography; TTE П­ transthoracic
echocardiography
incidence of aortic dissection is 5 to
T he30 estimated
cases per million people per year. This incidence is related to the prevalence of the risk factors
for aortic dissection in different study populations.1– 4 Complications often occur randomly, and
the outcome is frequently fatal. Many patients with
aortic dissection die before presentation to a hospital
or prior to diagnosis. The symptoms of aortic dissection may mimic myocardial ischemia, and physical
findings in aortic dissection may be absent or, if
present, could be suggestive of a diverse range of
other conditions. Therefore, keeping a high clinical
index of suspicion is crucial in establishing the
diagnosis of aortic dissection. The diagnosis of aortic
dissection has been missed in up to 38% of patients
*From the Division of Cardiology, Department of Medicine,
Creighton University School of Medicine, Omaha, NB.
Manuscript received December 20, 2000; revision accepted
October 18, 2001.
Correspondence to: Ijaz A. Khan, MD, FCCP, Creighton University Cardiac Center, 3006 Webster St, Omaha, NE 68131-2044;
e-mail: [email protected]
www.chestjournal.org
on initial evaluation, and in up to 28% of patients the
diagnosis has been first established at the post
mortem examination.1–3
Classification
Aortic dissection is divided into acute and chronic
types, depending on the duration of symptoms.
Acute aortic dissection is present when the diagnosis
is made within 2 weeks after the initial onset of
symptoms, and chronic aortic dissection is present
when the initial symptoms are of Пѕ 2 weeks duration. About one third of patients with aortic dissection fall into the chronic category.2 The most common site of initiation of aortic dissection is the
ascending aorta (50%) followed by the aortic regions
in the vicinity of the ligamentum arteriosum. Anatomically, aortic dissection has been classified by two
schemes. The DeBakey classification consists of the
following three types: I, both the ascending and the
descending aorta are involved; II, only the ascending
aorta is involved; and III, only the descending aorta
CHEST / 122 / 1 / JULY, 2002
311
is involved.5 The Stanford classification consists of
the following two types: type A, involving the ascending aorta regardless of the entry site location; and
type B, involving the aorta distal to the origin of the
left subclavian artery.6 Many cases of aortic dissection do not fit into these classification schemes. For
example, a dissection limited to the aortic arch
proximal to the origin of the left subclavian artery,
but not involving the ascending aorta, would not be
classified as type A or B. Therefore, it would be
prudent to simplify the classification of aortic dissection into proximal and distal types. Proximal aortic
dissection would be composed of the involvement of
the aorta proximal to the origin of the left subclavian
artery, which may or may not involve aortic segments
distal to that point, and distal aortic dissection would
be composed of the dissection limited to the aortic
segments distal to the origin of the left subclavian
artery and not involving the aorta proximal to that
point.
Predisposing Factors
Men are more frequently affected by aortic dissection, and a male/female ratio ranging from 2:1 to
5:1 has been reported in different series.7–10 The
peak age for the occurrence of proximal dissection is
between 50 and 55 years, and that of distal dissection
is between 60 and 70 years. Chronic systemic hypertension is the most common factor predisposing the
aorta to dissection and has been present in 62 to 78%
of patients with aortic dissection.1,2,11 At the initial
presentation, it is more common in patients with
proximal dissection than in those with distal dissection (70% vs 35%). Aortic diseases, such as aortic
dilatation, aortic aneurysm, anuloaortic ectasia, chromosomal aberrations (eg, Turner syndrome and
Noonan syndrome), aortic arch hypoplasia, coarctation of the aorta, aortic arteritis, bicuspid aortic
valve, and hereditary connective tissue diseases (eg,
Marfan syndrome and Ehlers-Danlos syndrome), are
well-established predisposing factors for the development of aortic dissection.4,12 Marfan syndrome
accounts for the majority of cases of aortic dissection
in patients ПЅ 40 years of age.
Direct iatrogenic trauma to the aorta that is
inflicted during arterial cannulation for cardiac surgery or during catheter-based diagnostic and therapeutic interventions accounts for about 5% cases of
aortic dissection.13,14 The majority of iatrogenic dissections have been reported in the descending thoracic and abdominal aorta.13,14 Reports13 suggest a
relationship between the severity of atherosclerosis
and the risk of developing an iatrogenic dissection.
In these cases, dissection may be initiated by cathe312
ter-related injury to the intima, which may previously have been weakened by atherosclerosis. On the
other hand, aortic atherosclerosis does not appear to
pose a high risk for classic spontaneous aortic dissection, but the development of its two variants, aortic
intramural hematoma and atherosclerotic aortic ulcer, is strongly associated with the presence and
severity of atherosclerosis.15 Indirect trauma, such as
sudden deceleration, also may result in dissection of
the aorta.
Cocaine has been recognized as a cause of aortic
dissection in otherwise healthy normotensive individuals.16,17 The proposed mechanism of aortic dissection during cocaine abuse is mediated through
catecholamine-induced, acute, profound elevation of
the BP, causing a rapid rise in the first derivative of
pressure (dP/dt) on the aortic wall resulting in an
intimal tear. Rebound acute elevation of BP secondary to the abrupt discontinuation of вђ¤-blocker therapy has also been reported as a cause of aortic
dissection, the mechanism of which could be the
same as that of the cocaine-induced aortic dissection.18 The risk of aortic dissection increases in the
presence of pregnancy. In women ПЅ 40 years of age,
50% of aortic dissections occur during pregnancy.
Hypertension has been reported in 25 to 50% of
cases of aortic dissection in pregnant women. The
most common site of pregnancy-associated aortic
dissection is the proximal aorta, and intimal tearing
originates within 2 cm of the aortic valve in 75% of
cases. The aortic rupture commonly occurs during
the third trimester or during the first stage of labor.
Pathogenesis
Aortic dissection can result from intimal rupture
followed by cleavage formation and propagation of
the dissection into the media, or from intramural
hemorrhage and hematoma formation in the media
subsequently followed by perforation of the intima.7
The rupture of the intima is the initial event in most
cases of dissection.7 The presence of an intimal flap
is the most characteristic feature of aortic dissection
(Fig 1). The pathogenesis of dissection is complex.
Reports19,20 have suggested that medial degeneration of the wall of the aorta predispose it to dissection by decreasing the cohesiveness of the layers of
the aortic wall. The medial degeneration tends to be
more extensive in older individuals and in patients
with hypertension, Marfan syndrome, and bicuspid
aortic valves.19,20
There is substantial physiologic evidence to suggest that intimal tears occur in the regions of the
aorta that are subjected to the greatest dP/dt and
pressure fluctuations.19 The repeated motion of the
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Figure 1. TEE view of the descending thoracic aorta in the
horizontal plane. An aortic dissection is manifested by the
presence of a true lumen (TL), a false lumen (FL), and a
free-floating intimal flap (F). LA П­ left atrium.
aorta related to the contractile function of the heart
results in flexion stress, which is most marked in
the ascending aorta and in the first portion of the
descending thoracic aorta, and these two sites are
the most common sites for the initiation of an intimal
tear. Furthermore, the hydrodynamic forces in the
bloodstream that are generated by the propagation
of a pulse wave and the generation of systolic BP
during each cardiac cycle deliver kinetic energy to
the aortic wall (most markedly to the ascending
aorta) during the systolic flow. A portion of this
kinetic energy is stored in the aortic wall as potential
energy, which then is used to propagate blood flow
in the aorta during the diastolic phase of the cardiac
cycle. The magnitude of the hydrodynamic forces in
the bloodstream is related to the mean BP and the
dP/dt, which represents the steepness of the pulse
wave. A combination of these factors eventually
results in an intimal tear and the propagation of
dissection into the media of the aortic wall, especially
so in patients with medial degeneration.
Aortic intramural hematoma is characterized by
aortic wall hematoma without a demonstrable intimal flap (Fig 2).20 –24 About 8 to 15% of cases of
acute aortic syndrome are of intramural hematoma.
The rupture of the vasa vasorum in the aortic wall is
the most likely cause of the development of aortic
intramural hematoma, which is contrary to most
cases of aortic dissection in which the intimal rupture
precedes the intramural cleavage in the previously
weakened aortic media.25 An intramural hematoma
also may result around the crater of a penetrating
atherosclerotic aortic ulcer and may propagate into
the media (Fig 3). Intramural hematoma formation
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Figure 2. TEE view of the descending thoracic aorta in the
horizontal plane. An aortic intramural hematoma is manifested by
the presence of a hematoma (H) in the aortic wall without an
intimal flap. L П­ aortic lumen.
is more common in the descending thoracic aorta. It
can perforate through the intima and transform into
a frank aortic dissection. Older, hypertensive patients with diffuse atherosclerosis are more prone to
develop aortic intramural hematomas.
Penetrating atherosclerotic aortic ulcers typically
occur in elderly patients who have histories of hypertension, hyperlipidemia, and severe aortic atherosclerosis.26 These ulcers are most common in the
descending thoracic aorta. They are characterized by
a discrete ulcer crater and by a thickened underlying
aortic wall (Fig 3). Progressive penetration deep into
the aortic wall may result in an intramural hematoma
and a weakening of the aortic wall, which, in turn,
Figure 3. TEE view of the descending thoracic aorta in the
longitudinal plane. An atherosclerotic aortic ulcer (U) is manifested by the presence of a crater with overhanging borders in the
atherosclerotic plaque. An intramural hematoma originates from
the ulcer with propagation into the aortic wall. See the legend of
Figure 2 for abbreviations not used in text.
CHEST / 122 / 1 / JULY, 2002
313
may result in aortic enlargement and aneurysm
formation.27 Spontaneous healing of the ulcer and
resolution of the associated intramural hematoma
may cause remodeling in the aortic wall, which also
may result in aortic dilatation.
Natural History
The natural history of aortic dissection is poorly
understood. Earlier information on aortic dissection
was gained mostly from autopsy studies, while newer
clinical or pathologic studies came from large referral centers and were based on selected nonconsecutive cases.1 Acutely, the hydrodynamic forces in the
bloodstream continue the propagation of the dissection in the media at varying depths until a rupture
occurs either into the lumen of the aorta, resulting in
the reduplication of the aortic lumen, or out through
the adventitia of the aorta, causing death. Aortic
dissection in the ascending aorta is usually to the
right and posterior just above the level of the right
coronary artery ostium. As a dissecting hematoma
advances into the arch of the aorta, it passes posteriorly and superiorly. The dissection is most common
posterior and to the left in the descending thoracic
and abdominal aorta, resulting in a higher incidence
of involvement of the left renal and the left iliofemoral arteries than of those of the right.
According to the results of a population-based
longitudinal study on the epidemiology and clinicopathology of aortic dissection by Meszaros et al,28
21% of patients with aortic dissections die before
hospital admission. The mortality rate for patients
with untreated proximal aortic dissections has been
reported to increase by 1 to 3% per hour after
presentation and is approximately 25% during the
first 24 h after the initial presentation, 70% during
the first week, and 80% at 2 weeks.9,14,29 Less than
10% of untreated patients with proximal aortic dissections live for 1 year, and almost all patients die
within 10 years.28 Most of these deaths occur within
the first 3 months. According to earlier data (collected from six series) reported by Anagnostopoulos et
al30 on 963 untreated patients with aortic dissections,
90% died within 3 months of presentation with the
condition. Death usually is caused by acute aortic
regurgitation, major branch vessel obstruction, or
aortic rupture. The risk of the fatal aortic rupture in
patients with untreated proximal aortic dissections is
around 90%, and 75% of these ruptures take place in
the pericardium, the left pleural cavity, and the
mediastinum.31
The natural history of aortic intramural hematoma
is similar to that of the classic aortic dissection. The
morbidity and mortality of patients with aortic intra314
mural hematoma depends on the site of aortic
involvement.32–36 An aortic intramural hematoma
may cause an intimal rupture and transform into a
frank aortic dissection. Besides resulting in an intimal tear and transforming into a dissection, an aortic
intramural hematoma can penetrate deep into the
layers of the aortic wall, resulting in a rupture or
pseudoaneurysm of the aorta. The prevalence of
fluid extravasation into the pericardial, pleural, or
mediastinal space is high and indicates impending
aortic rupture.37 Spontaneous resolution of an aortic
intramural hematoma also has been reported.38
The natural history of atherosclerotic aortic ulcers
is of progressive penetration into the internal elastic
lamina and media with a propensity toward aortic
dilatation and aneurysm formation.26 Further progressive penetration of theses ulcers also may result
in aortic dissection, aortic rupture, and pseudoaneurysm formation. Aortic dissection is an uncommon
consequence of the atherosclerotic aortic ulceration,
even though reports have described rare initiation of
an aortic dissection at the base of an aortic atherosclerotic ulcer.39,40 While some degree of hematoma
occurs around most atherosclerotic aortic ulcers,
propagation to frank dissection is prevented, probably because of the extensive fibrosis of the aortic wall
from long-standing atherosclerosis.22 On long-term
follow-up, atherosclerotic aortic ulcers tend to cause
aortic dilatation and aneurysm formation more than
frank aortic dissections. A free transmural rupture of
the aorta is rare. Similarly, a thromboembolism
resulting from atherosclerotic aortic ulcers is also
rare.26
Manifestations
Pain in Aortic Dissection
Pain is the most common presenting symptom of
aortic dissection. The pain of an aortic dissection is
midline and is experienced in the front and back of
the trunk, depending on the location of the dissection. The onset of pain is typically catastrophic, and
it reaches a maximum level suddenly. The pain could
be sharp, ripping, tearing, or knife-like in nature, but
the abruptness is the most specific characteristic of
the pain. The pain of aortic dissection does not
commonly radiate into the neck, shoulder, or arm, as
is typical of the pain of an acute coronary syndrome.
According to a report1 on 464 patients from the
International Registry of Acute Aortic Dissection,
95% of patients reported any pain, and 85% reported
an abrupt onset. Sharp pain was reported by 64% of
patients, whereas the classic tearing or ripping type
of pain was reported by 51% of patients. The most
common site of pain was the chest (73%), with
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anterior location being more common than the
posterior location (61% vs 36%, respectively). Back
pain was experienced by 53% of patients, and abdominal pain was experienced by 30% of patients.
Patients with dissections of the ascending aorta and
arch more frequently experience anterior chest pain,
whereas patients with dissections of the descending
aorta more frequently experience posterior chest, back,
and abdominal pain. Extension of the pain down to the
back, abdomen, hips, and legs indicates the extension
of the dissection process distally. According to a published analysis,41 the physicians’ index of suspicion was
highest (86%) in patients who presented with both
chest and back pain, followed by those with chest pain
(45%) and abdominal pain (8%). The aortic dissection
also has been diagnosed on an incidental imaging study,
such as transesophageal echocardiography (TEE), CT
scan, or MRI that were performed for other reasons.42– 44 There is a possibility that the pain in these
patients could have been minimal, and may have been
ignored, or that the dissection could have been truly
silent. The initial pain of aortic dissection may be
followed by a pain-free interval lasting from hours to
days, ending with the return of pain. This return of pain
after a pain-free interval is an ominous sign and usually
indicates an impending rupture.28
Manifestations Secondary to Organ System
Involvement
More than one third of the patients with aortic
dissections demonstrate signs and symptoms secondary
to organ system involvement.45 The most common
mechanism of organ system involvement is the development of ischemia caused by the obstruction of
branch arteries originating from the aorta. A branch
vessel obstruction could be due to an extension of the
dissection process into the wall of the artery or due to
a direct compression of the artery by an expanding false
lumen. Another mechanism of organ system involvement in the process of aortic dissection is the direct
compression of a surrounding organ by the expanding
false lumen of the dissection. Compressive manifestations are more prone to take place in cases in which the
false lumen is not decompressed by a distal intimal tear
and results in an expanding blind loop. A third mechanism of organ system involvement in patients with
aortic dissection is a leak or rupture of the dissection
process into the surrounding structures, which is usually rapidly fatal. The two most commonly involved
organ systems in the process of aortic dissection are the
cardiovascular and neurologic systems.
Cardiovascular Involvement: Aortic regurgitation
(of any degree) accompanies 18 to 50% of cases with
proximal aortic dissection.11,46 A diastolic murmur of
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aortic regurgitation has been reported in about 25%
of patients. Acute, severe aortic regurgitation is the
second most common cause of death (after aortic
rupture) in patients with aortic dissections. Patients
with this condition usually present with acute cardiac
decompensation and shock.3 The mechanisms of
aortic regurgitation in aortic dissection include dilatation of the aortic root and annulus, tearing of the
annulus or valve cusps, downward displacement of
one cusp below the line of the valve closure (due to
pressure from an asymmetric false lumen), loss of
support of the cusp, and physical interference in the
closure of the aortic valve by an intimal flap.
Although most patients with aortic dissections
have hypertension at the time of presentation, an
initial systolic BP ПЅ 100 mm Hg has been reported
in about 25% of patients with aortic dissections.
Hypotension and shock in patients with aortic dissections are caused by acute severe aortic regurgitation, aortic rupture, cardiac tamponade, or left ventricular systolic dysfunction.47,48 A rupture or leak of
the dissection process into the pericardial cavity may
result in acute pericardial effusion/cardiac tamponade and death.48 Nevertheless, in most cases of aortic
dissection, the development of a pericardial effusion
is not secondary to the rupture or leak of the
dissection into the pericardial cavity, rather it is due
to the transudation of fluid into the pericardial cavity
through the intact wall of the false lumen.49 Although the presence of pericardial effusion in patients with aortic dissections is not always secondary
to the rupture or leak of the dissection process into
the pericardial cavity, the presence of any pericardial
effusion may be a very ominous sign and should be
taken seriously.
Left ventricular regional wall motion abnormalities are seen in 10 to 15% of patients with aortic
dissections and are primarily caused by low coronary
perfusion. The presence of low coronary perfusion in
patients with aortic dissections could be secondary to
the compression of a coronary artery by the expansion of a false lumen, the extension of the dissection
process into a coronary artery, hypotension, or a
combination of these conditions.4 Involvement of the
right coronary artery is more common than that of
the left one, and occasionally dissection and myocardial infarction occur concomitantly.46 Myocardial
ischemia with resultant left ventricular systolic dysfunction is a factor contributing to the development
of hypotension and shock in patients with aortic
dissections.
A myriad of manifestations develop due to pressure of the false lumen or its rupture into the
surrounding cardiac chambers or great vessels.50,51
The pulse deficits reported in patients with aortic
dissections include a significant difference in the
CHEST / 122 / 1 / JULY, 2002
315
pulse volume (ie, pulse differentials) and BP (ie, BP
differentials) in two upper extremities or a sudden
loss of a pulse. The presence of pulse differentials is
the most specific physical sign of aortic dissection,
and it has been reported in 38% of patients with
aortic dissections.52 Pulse and BP differentials indicate the partial compression of one or both subclavian arteries. Due to the partial compression or the
presence of oscillating flaps, bruits may be present
over major arteries, such as the carotid, subclavian,
and femoral arteries. Symptomatic ischemia of an
extremity, mostly lower extremities, has been reported in 15 to 20% of patients with aortic dissections.53–56 The abrupt onset of chest pain with the
sudden loss of pulse or blood flow to a lower
extremity should raise a high suspicion of aortic
dissection. The duplication of pulse is a rare physical
finding in patients with aortic dissections and is
probably due to the difference in flow rates in the
true and false channels in cases in which a false
lumen reenters the true lumen.57 An examination of
the neck may reveal unilateral vein distension resulting from obstruction secondary to the expanding
false lumen around the aorta or from bilateral vein
distension due to obstruction of the superior vena
cava or from cardiac tamponade. Rare cases of right
atrial compression, pulmonary artery obstruction,
and aorto-right atrial fistula formation have been
reported in the literature.58 – 60
Neurologic Involvement: Neurologic deficits have
been associated with 18 to 30% cases of aortic
dissection.61,62 Cerebral ischemia/stroke is the most
common neurologic manifestation associated with
aortic dissection and has been reported to affect 5 to
10% of patients.61– 63 Most patients with aortic dissections who present with stroke also reveal a history
of chest pain. Besides stroke, the altered cerebral
perfusion may cause symptoms of transient cerebral
hypoperfusion ranging from altered mental status to
syncope, and among patients with proximal aortic
dissection, up to 12% may present with syncope.64
Spinal cord ischemia and ischemic peripheral neuropathies are more common with distal aortic dissections, and spinal cord involvement has been reported
in up to 10% of these cases.61 Spinal cord involvement in patients with aortic dissections could be
secondary to the occlusion of the intercostal arteries,
the artery of Adamkiewicz, or the thoracic radicular
arteries. A spinal cord watershed area found between
the territories of the artery of Adamkiewicz and the
thoracic radicular artery is more prone to ischemic
damage from aortic dissection.65 Spinal cord involvement in aortic dissection results in various spinal
cord syndromes, including transverse myelitis, progressive myelopathy, spinal cord infarction, anterior
316
spinal cord syndrome, paraplegia, and quadriplegia.65– 68
The involvement of the peripheral nerves in cases
of aortic dissection is due to neuronal ischemia or to
the direct compression of a nerve by the false lumen.
Although peripheral nerve involvement in patients
with aortic dissection is rare, it may result in protean
neurologic symptoms, including paresthesia in the
limbs, hoarseness of voice, ischemic lumbosacral
plexopathy, and Horner syndrome.69 –71 Most of the
patients with aortic dissections who display the
symptoms of neurologic involvement present with
pain, but there are reports in the literature in which
various neurologic symptoms, such as stroke, syncope, or hoarseness of voice, were the initial presenting features of the aortic dissection.63–71
Pulmonary Involvement: Pulmonary manifestations of aortic dissection are rare. The left pleural
space is the most common space where the descending thoracic aortic dissection leaks.72,73 Painless aortic dissection may be considered in the differential
diagnosis of the unexplained, nontraumatic, leftsided hemorrhagic pleural effusion. Rare cases have
been described in which the dissection eroded into
or compressed the pulmonary artery or lung parenchyma, resulting in severe hemodynamic compromise, unilateral pulmonary edema, or hemoptysis.74 –76
GI Involvement: Acute GI hemorrhage is a very
rare presentation of the dissection of the descending
aorta and has been limited to a few case reports.77–79
Acute GI hemorrhage has resulted from erosion of
the esophagus or duodenum.77,78 Extension of the
dissection into the mesenteric arteries has resulted in
an acute abdomen.80 Rarely, esophageal compression from the false lumen of aortic dissection has
resulted in dysphagia.81,82
Clinical Prediction of Aortic Dissection
von Kodolitsch et al52 devised a clinical prediction
model for the initial prediction of aortic dissection
based on history, physical findings, and chest radiography findings. In this study, 250 patients with
acute chest pain, back pain, or both, and clinical
suspicion of acute aortic dissection were examined
for the presence of 26 clinical and radiographic
variables by using multivariate analysis. The independent predictors of aortic dissection were identified as follows: chest pain with immediate onset, a
tearing or ripping character, or both; pulse differentials, BP differentials, or both; and mediastinal widening, aortic widening, or both. The assessment of
these three variables permitted the identification of
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96% of acute aortic dissection cases. The probability
of dissection was high (ie, Х† 83%) with isolated pulse
or BP differentials, or any combination of the three
variables, intermediate with isolated findings of aortic pain (31%) or mediastinal widening (39%), and
probability was low (7%) with the absence of all
three variables. This simple clinical model could be
useful for a rapid assessment of the initial prediction
of aortic dissection tailoring the prompt institution of
confirmatory diagnostic imaging.
Diagnosis
The diagnosis of aortic dissection begins with
clinical suspicion, which is the most crucial step in
diagnosing this catastrophic disease. The next two
important steps in the evaluation of patients with
suspected aortic dissection are to confirm the presence of dissection and to differentiate between
proximal and distal dissections. This information is
critical, not only for deciding whether surgery is
indicated, but also for deciding on the site for
surgical access. The diagnosis should be confirmed
rapidly and accurately, preferably with an easily
available noninvasive modality. The planning for a
therapeutic strategy depends not only on the type of
dissection but also on the site of entry, the extent of
dissection, the involvement of the coronary arteries,
arch branches, or visceral arteries, the involvement
of the aortic valve, the presence and extent of
pericardial effusion, false lumen patency, and the
presence of thrombus in the false lumen. Therefore,
delineation of these features should be an important
part of the diagnostic workup for patients with
suspected aortic dissections.83
Chest radiography lacks the specificity for a diagnosis of aortic dissection. Similarly, ECG changes are
nonspecific (chiefly, nonspecific ST-segment/T-wave
changes), even though two thirds of patients with
aortic dissections harbor these changes. CT scanning, MRI, and TEE are highly accurate techniques
that are useful for the diagnosis of aortic dissection.
Transthoracic echocardiography (TTE) has limited
diagnostic accuracy. Aortography is invasive, and
serial studies are difficult due to the need of frequent
femoral arterial punctures. Studies (reported later in
this article) have demonstrated the existence of a
serum biochemical marker (ie, smooth muscle myosin heavy chain marker) that is helpful in diagnosing
aortic dissection.
Imaging Techniques
Aortic dissection may become fatal rapidly if left
undiagnosed and untreated. Therefore, the choice of
the initial imaging modality used to diagnose aortic
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dissection depends chiefly on the availability of a
particular modality in the facility. The imaging modalities that are useful for the diagnosis of aortic
dissection are CT scanning, MRI, TEE, and angiography. In various studies, each of these imaging
techniques has been reported to have high sensitivity, specificity, diagnostic accuracy, and positive and
negative predictive values. However, these values
may vary significantly based on the prevalence of
aortic dissection in the study population and are
likely to be more applicable in the high-risk patients.
Using Bayes theorem, Barbant et al84 calculated the
predictive values and accuracies of different imaging
techniques for thoracic aortic dissection. In high-risk
patients (ie, disease prevalence, 50%), the positive
predictive values were Пѕ 85% for all four diagnostic
modalities (ie, CT scanning, MRI, TEE, and aortography). However, for intermediate-risk patients (ie,
disease prevalence, 10%), the positive predictive
values were Пѕ 90% for CT scanning, MRI, and TEE
but was 65% for aortography. In low-risk patients (ie,
disease prevalence, 1%), the positive predictive values were ПЅ 50% for CT scanning, TEE, and aortography but was close to 100% for MRI. However, in
all three types of patient populations, the negative
predictive values and accuracies were Пѕ 85% for all
four diagnostic modalities.
Chest Radiography: Although chest radiography
lacks specificity for the diagnosis of aortic dissection, it
could be of value for the initial prediction of the disease
when used in combination with history and physical
examination findings. The classic radiographic sign that
is suggestive of aortic dissection is the widening of the
mediastinal shadow, which has been reported in up to
50% of cases of aortic dissection. The mediastinum
bulges to the right with dissection of the ascending
aorta, and to the left with dissection of the descending
thoracic aorta.85,86 The other chest radiographic signs
reported in patients with aortic dissection are altered
configuration of the aorta, a localized hump on the
aortic arch, a widening of the distal aortic knob past the
origin of the left subclavian artery, aortic wall thickness
indicated by the width of the aortic shadow beyond
intimal calcification, displacement of the calcification in
the aortic knob, a double aortic shadow, disparity in the
sizes of the ascending and descending aortas, and
the presence of a pleural effusion, most commonly on
the left.85,86 These radiographic signs are suggestive of,
but not diagnostic of, aortic dissection.
CT Scanning: CT scanning was the most common
initial diagnostic test that was performed in the
patients enrolled in the International Registry of
Acute Aortic Dissection, probably because it is less
invasive and allows rapid diagnosis in emergency
CHEST / 122 / 1 / JULY, 2002
317
situations.1,87 Sensitivities of 83 to 94% and specificities of 87 to 100% have been reported with the use
of CT scanning for the diagnosis of aortic dissection
except in cases of dissection of the ascending aorta,
in which its sensitivity is Ͻ 80%.88 –91 The main
disadvantages of the use of CT scanning, besides
problems from the use of contrast material, are the
following: difficulty in identifying the origin of the
intimal tear; difficulty in assessing the involvement of
aortic branch vessels; and inability to provide information about aortic valve regurgitation.83
Helical CT scanning is considered to be superior
to conventional CT scanning for the detection of
aortic dissection because in helical CT scanning
more images are obtained during the peak levels of
enhancement due to better tracking of the contrast
material bolus.92,93 Helical CT scanning also is associated with a higher rate of detection and better
evaluation of lesions when there is respiratory motion along the patient’s longitudinal axis. Furthermore, high-quality two-dimensional and threedimensional reconstructions, which in turn are
useful for the visualization of the course of the
dissection membrane in the aortic arch relative to
the origin of the subclavian artery, are possible with
the use of helical CT scanning.94,95 In distal dissections, this information is especially important to rule
out the presence of retrograde dissection into the
aortic arch, which may take place in 27% of cases of
distal dissection and is associated with substantially
higher mortality rates of up to 43%. Helical CT
scanning is fast and easy to perform, and is probably
the least operator-dependent imaging modality that
is available for the detection of aortic dissection. It
also allows better comparisons on follow-up studies,
provided that the measurements are made in welldefined planes. However, the experience with the
use of helical CT scanning is limited, and its role in
the diagnosis of aortic dissection needs to be defined
further.
MRI: Both the sensitivity and the specificity of
MRI are in the range of 95 to 100%.96 –102 The MRI
can detect aortic dissection accurately, can delineate
the extent of the dissection, can demonstrate the site
of the entry tear, can identify the arch vessels that
are involved, and can assess the renal artery involvement. Spin echo ECG-gated sequences can help to
identify slow flow within the false lumen. Cine and
gradient recall echo sequences also provide useful
dynamic information about the flow within the two
lumens. Dynamic turbo flash-enhanced imaging can
provide additional data when the results obtained
with spin echo and cine sequences are inconclusive
due to the presence of thrombus or lack of flow.96
MRI is also well-suited for the evaluation of preex318
isting aortic disease, valvular involvement, and previous surgical repair.97–102 In the studies that compared MRI with TEE or CT scanning,97–102 the
sensitivity and specificity of MRI was higher among
the patients with previous aortic disease. In addition,
the MRI has the capability to perform the threedimensional reconstruction of the images in any
plane.
The limitations of MRI include the lack of immediate availability, the delay from bedside to scanner,
the long examination time, the limited access to the
patient, and the restricted monitoring of vital signs,
which is especially problematic in hemodynamically
unstable patients, although the latter has improved
since the advent of the short-bore MRI units.103
Furthermore, it is not safe for patients with cardiac
pacemakers, ferromagnetic aneurysm or hemostatic
clips, and ocular or otologic implants to undergo
MRI examinations. With the advent of MRI sequences such as the breath-hold gradient-echo and
fast-gradient echo sequences, and segmental
K-space acquisition, the procedure time can be
reduced to ПЅ 5 min without compromising high
accuracy.
TTE: The sensitivity and specificity of TTE for the
detection of aortic dissection range from 35 to 80%
and 39 to 96%, respectively, depending on the
anatomic location of the dissection.104 –107 On transthoracic M-mode echocardiography, floating intimal
membranes, the enlargement of the aortic root, the
enlargement of the aortic arch, and an increase in the
aortic wall thickness were the initially described
signs of aortic dissection. With the introduction of
two-dimensional echocardiography and the feasibility of taking suprasternal, subcostal, and substernal
views, it has become possible to directly visualize the
ascending aorta and aortic arch for floating intimal
membranes, intimal tears, and false lumens. However, despite these efforts, an analysis of the aorta by
TTE remains difficult due to technical limitations,
narrow intercostal spaces, obesity, and pulmonary
emphysema. False-positive results have been observed in patients with dilated ascending aortas in
whom artifacts from reverberations may appear like
membranes. Although color flow Doppler studies
could be of help in these cases, since no differential
flow would be seen as expected in a false lumen in
patients with aortic dissections, the TTE is by no
means a conclusive test for ruling out the possibility
of aortic dissection, even in the ascending aorta.
TEE: TEE is widely available, is safe in experienced hands, and can be performed quickly and
easily at the bedside. These advantages make TEE
ideal for use in most patients with aortic dissections,
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including relatively unstable patients. The sensitivity
of TEE has been reported to be as high as 98%, and
the specificity ranges from 63 to 96%.108 –116 Furthermore, TEE possesses the ability to identify the
following: the entry site of dissection; the presence of
thrombus in a false lumen; abnormal flow characteristics; the involvement of coronary and arch vessels;
the presence, extent, and hemodynamic significance
of pericardial effusion; and the presence and severity
of aortic valve regurgitation. The most important
diagnostic finding of aortic dissection that can be
seen on TEEs is the presence of an undulating
intimal flap within the aortic lumen that differentiates a false lumen from a true lumen. In order to
avoid a false-positive diagnosis, the intimal flap has to
be identified in more than one view, and it should
have motion that is independent from that of the
aortic wall. Furthermore, different color flow Doppler patterns should be visible in the two lumens. In
cases in which the false lumen has undergone thrombosis, a central displacement of the intimal calcification and a thickening of the aortic wall may suggest
the presence of aortic dissection.117 The possibility of
aortic dissection is increased if, in addition to the
intimal flap, an entry site, color Doppler flow and/or
thrombus in the false lumen, or aortic root dilation is
seen.
The main limitations of TEE are its strong dependence on the investigator’s experience and the difficulty in objectively documenting the pathologic findings for comparison with follow-up studies. The field
of view is limited to the thoracic and proximal
abdominal aorta, thus the distal extension of the
dissection below the celiac trunk cannot be visualized by TEE. Furthermore, TEE cannot be performed in patients with esophageal varicosity or
stenosis.118 The study could also result in a falsenegative finding due to the presence of an echocardiographic blind spot in the distal ascending aorta
and proximal aortic arch secondary to the position of
the air-filled trachea and left mainstem bronchus
interposed between the esophagus and this part of
the aorta.110 –112 False-positive results could occur as
a result of reverberation echoes, fat-shift artifacts
from the mediastinum, motion artifacts originating
from the aneurysmal ascending aorta, calcified atheromatous plaque, and/or, in postoperative cases,
periaortic hematoma.119 –122 A false-positive diagnosis not only mandates an urgent surgical intervention
that requires full cardiopulmonary bypass and hypothermic circulatory arrest if arch involvement exists,
but also deprives the patient of proper and timely
treatment of the true disease. Supplementing TEE
findings with additional imaging studies may improve diagnostic accuracy, especially in cases in
which TEE findings are considered to be probable
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for the presence of aortic dissection and the clinical
suspicion of aortic dissection is high.122
Aortography: Aortography has a sensitivity of 86 to
88% and a specificity of 75 to 94% for the diagnosis
of thoracic aortic dissection.123–126 It has long been
considered the procedure of choice for the patients
with suspected aortic dissection, but these days,
because of being invasive and time-consuming, aortography rarely is used as the initial diagnostic
procedure to detect aortic dissection. The aortographic findings seen in patients with aortic dissection include the splitting or distortion of the contrast
column, flow reversal or stasis, altered flow pattern,
the failure of major vessels to fill, and aortic valve
insufficiency. Although coronary angiography in association with aortography may delineate coronary
anatomy, especially when coronary artery involvement in a dissection is suspected, caution should be
used in unstable patients for whom the coronary
angiography may be dangerous due to the imposed
delay of the surgical intervention.
Serum Smooth Muscle Myosin Heavy Chain
Interestingly, some studies127–130 have demonstrated the existence of a serum biochemical marker
of aortic dissection. Aortic dissection causes extensive damage to the smooth muscle cells of the media,
leading to the release of structural proteins of the
smooth muscle cells including smooth muscle myosin heavy chain into the circulation. An immunoassay
to detect serum smooth muscle myosin heavy chain
has been developed and is being tested as a potential
tool that would be useful for the early detection of
aortic dissection.127–130 Serum levels of smooth muscle myosin heavy chain elevate significantly within
the first 6 h after the onset of aortic dissection.129,130
Cross-reactivity of the smooth muscle myosin heavy
chain assay with the cardiac and skeletal muscle is
ПЅ 0.05%, but the cross-reactivity against uterine
myosin is 100%. The mean (П® SD) smooth muscle
myosin heavy chain level in normal human sera taken
from healthy individuals was 0.9 П® 0.4 вђ®g/L.129 The
clinical decision limit has been set at 2.5 вђ®g/L.
According to a report by Suzuki et al,130 the serum
values of smooth muscle myosin heavy chain were
significantly higher in 95 patients with aortic dissection
compared with 131 healthy volunteers (22.4 П®
40.4 вђ®g/L vs 0.9 П® 0.4 вђ®g/L, respectively; p ПЅ 0.001).
The highest levels (51.0 П® 52.3 вђ®g/L) were seen in 33
patients who presented within 3 h after the onset of
symptoms. In 48 patients with acute myocardial infarctions, the mean serum levels of smooth muscle myosin
heavy chain were 2.1 П® 1.6 вђ®g/L (p ПЅ 0.001 [compared with patients with aortic dissections]). The serum
CHEST / 122 / 1 / JULY, 2002
319
levels of smooth muscle myosin heavy chain were
higher in patients with proximal aortic dissections than
in those with distal aortic dissections (p П­ 0.03), probably because the thoracic aorta has more smooth
muscle than the abdominal aorta. In 33 patients with
acute aortic dissections who presented within 3 h after
the onset of symptoms, the sensitivity of the assay was
91% and the specificity of the assay was 98% compared
with 131 healthy volunteers, and the specificity of aortic
dissection was 83% compared with 48 patients who had
acute myocardial infarctions. The diagnostic accuracy
was 96%. The sensitivity of the assay decreased to 72%
in next 3-h period and decreased to 30% thereafter.
Serum levels of smooth muscle myosin heavy chain of
Пѕ 10 вђ®g/L showed 100% specificity for aortic dissection. The time taken to run the assay was 30 min.
Thus, the biochemical diagnosis of acute aortic
dissection is rapid, can be established by a noninvasive test, and appears to be highly sensitive and
specific. Once it is investigated further and becomes
available on a commercial basis, it may become a
useful initial step in triaging the patients with suspected aortic dissection, provided that patients
present within 6 h, and preferably within 3 h, after
the onset of symptoms. The assay also may help in
judging the need for and urgency of performing
additional diagnostic procedures.
Special Diagnostic Considerations
Differentiation of Aortic Dissection and Degenerative Aortic Disease: Aortic atherosclerosis is usually
more obvious and the surface of the plaque is usually
rough compared to the smooth delineation of the
intimal flap. Mural thrombi are seen only in the
dissection. However, it should be remembered that a
rupture of aortic plaques could lead to aortic ulceration and dissection.
Differentiation of the True and False Lumens:
Spontaneous echo contrast is usually visualized in a
false lumen and is related to slow or delayed
flow.109,115,131 Compared to systolic forward flow in
the true lumen, delayed or even reversed flow may
be seen in the false lumen. However, the degree of
color flow visualization in the false lumen is dependent on the extent of communication of the false
lumen with the true lumen; when this communication is reduced or absent, color flow within the false
lumen is reduced or absent as well. Moreover, the
thrombus formation is only noted in the false lumen.
Localization of Intimal Tears: Intimal tears can be
visualized directly by both MRI and TEE.108,114
Usually, patients have both entry and reentry tears
and, in addition, may have multiple intermediary
320
tears.115 Flow across the tear is often bidirectional,
and variable flow patterns can be seen during a long
diastole. The pressure gradient at the entry tear is
rarely of substantial magnitude since the pressure in
the false lumen is systemic.
Communicating and Noncommunicating Dissection: Noncommunicating dissections are rare (ie,
ПЅ 10% of cases). They can be differentiated from
communicating dissections by visualizing the flow in
the false lumen and by detecting both the entry and
exit tears in the intimal flap.115,131 The filling of the
false lumen with thrombus is found more often in
patients with noncommunicating dissections. Therefore, differentiation between the intramural hematoma and a small noncommunicating dissection
sometimes may be difficult to establish.131
Aortic Regurgitation: Since aortic regurgitation is
present in up to 50% of patients with proximal aortic
dissection, the determination of the degree of severity and the pathophysiologic mechanisms involved in
the causation of the regurgitation is important for the
planning of the surgical intervention in these cases.132 Both TTE and TEE can provide valuable
information in this regard. Color Doppler studies
have high sensitivity and specificity for the visualization and semiquantitative analysis of aortic regurgitation.133
Side Branch Involvement: Myocardial ischemia
and infarctions that are related to aortic dissection
contribute significantly in the perioperative mortality
of aortic dissections.134 The development of a new
regional wall motion abnormality in the left ventricle
could be a sign of involvement of a coronary artery in
the dissection process. Direct evidence of coronary
involvement may be present during TEE with the
intimal flaps seen in the ostium of the right or left
coronary arteries. In unstable patients with aortic
dissections for whom coronary angiography may be
dangerous due to the imposed delay of surgical
intervention, these echocardiographic findings may
be especially helpful.135,136 Knowledge of the involvement of the aortic arch vessels, renal arteries,
and iliofemoral arteries is important for surgical
planning. MRI and vascular sonography with duplex
scanning are two useful techniques for studying
these vessels.
Blood Extravasation: The extravasation of blood in
the pericardium, pleural space, or mediastinum often
signals an emergency because of the high likelihood of
the penetration or rupture of the dissection into these
spaces.115,131 Echocardiography, CT scanning, and
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MRI are all highly accurate in identifying blood accumulation in the pericardium, pleural space, or mediastinum. The compression of cardiac chambers by mediastinal hematoma also can be detected accurately by all
three of these techniques. The TTE is the procedure of
choice to rule out cardiac tamponade. Extravasation of
blood into the pleural space also can be diagnosed by
chest radiography.
Intramural Hemorrhage and Hematoma: The diagnostic features of intramural hemorrhage are the
presence of multiple layers of the aortic wall with
splitting due to hemorrhage and increasing wall
thickness (ie, Пѕ 0.5 cm), as manifested by an increase in the distance from the aortic lumen to the
esophagus.137 Both TEE and MRI can detect intramural hemorrhage and hematoma accurately. The
diagnostic features of intramural hematoma on TEE
include the following: localized thickening of the
aortic wall; intramural echo-free spaces; the absence
of the dissection membrane, communication or
Doppler flow signal; and the central displacement of
intimal calcification.137–139 MRI has a unique capability not only of diagnosing intramural hematoma,
but also of detecting serial pathologic changes taking
place within the hematoma, which may be helpful in
identifying the progression or regression of a hematoma on follow-up studies. MRI also possesses the
ability to assess the age of the hematoma based on
the formation of methemoglobin.140 High-intensity
signals on both T1-weighted and T2-weighted images produced by methemoglobin indicate the subacute nature of the intramural hematoma, whereas
recent bleeding results in signals of different intensities within various regions of the hematoma.33–35
Atherosclerotic Aortic Ulcer: CT scanning was the
initial imaging study established as an accurate modality for imaging penetrating atherosclerotic aortic
ulcers. However, such imaging requires the optimal
contrast filling of the aortic lumen and ulcer crater.25,141 MRI has shown higher accuracy to detect
penetrating atherosclerotic aortic ulcers when compared with contrast-enhanced CT scanning and
could be of particular value when contrast injection
is contraindicated.23,142 Although the utility of TEE
for the diagnosis of penetrating atherosclerotic aortic
ulcers has been well-documented, the ulcers present
at the level of the echocardiographic blind spot in the
distal ascending aorta and the proximal part of the
aortic arch could be missed on TEE.24,119,143
Follow-up Studies: About 15% of patients with
aortic dissections who are treated surgically require a
second operation because of the progression of an
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existing dissection, the development of a new dissection, or the formation of an aortic aneurysm. New
dissections may develop at the anastomosis sites or at
the aortic parts not involved before. Both TEE and
MRI allow imaging of the Dacron prosthesis and
anastomosis sites as well as of the other parts of the
aorta that were not involved previously.115,131 Similarly, both procedures can detect aortic dilatation
and aneurysm formation on follow-up studies.
Treatment
Medical Treatment
IV antihypertensive treatment should be started
emergently in all patients, except in those with
hypotension, as soon as the diagnosis of acute aortic
dissection is suspected. The aims of the medical
therapy are to reduce the force of the left ventricular
contractions, to decrease the steepness of the rise of
the aortic pulse wave (ie, dP/dt), and to reduce the
systemic arterial pressure to as low a level as possible
without compromising perfusion to the vital organs.
In the experimental models of dissection, laminar
nonpulsatile flow is associated with the cessation of
the advancement of dissection, whereas pulsatile
flow of increasing acceleration results in the continuation of dissection in both directions from the initial
intimal tear. Therefore, reducing the rate of rise of
the aortic pulse by decreasing the force of the left
ventricular contractions would retard the propagation of the dissection and decrease the risk of aortic
rupture.
Historically, in the early 1960s, Wheat et al144
introduced drug therapy for aortic dissection by
originally using reserpine and guanethidine. At the
present time, a combination of a вђ¤-blocker and a
vasodilator (ie, sodium nitroprusside) is a standard
medical therapy used in patients with aortic dissections. вђ¤-blocker therapy should be instituted before
starting sodium nitroprusside therapy. Otherwise,
the reflex catecholamine release secondary to the
direct vasodilatation caused by sodium nitroprusside
may result in an increase in the left ventricular
contraction force and aortic pulse dP/dt, resulting
in propagation of the dissection.19 Labetalol, an
вђЈ-adrenergic and вђ¤-adrenergic antagonist, is an alternative to the combination of a вђ¤-blocker and
sodium nitroprusside.145 Trimethaphan, a ganglionic
blocker as well as a direct vasodilator, can be used
when the above-mentioned agents are ineffective,
poorly tolerated, or contraindicated. Trimethaphan
would serve to decrease both the aortic pulse dP/dt
and the systemic BP. However, the efficacy of
trimethaphan is less predictable than that of sodium
nitroprusside, and it may cause tachyphylaxis, severe
hypotension, urinary retention, and ileus.
CHEST / 122 / 1 / JULY, 2002
321
Patients with uncomplicated distal aortic dissections can be managed medically in the acute phase,
as the survival rate is around 75% whether patients
are treated medically or surgically.146 Furthermore,
patients with distal dissections are usually older and
often are experiencing concomitant cardiac, pulmonary, and/or renal diseases. Also, those patients with
proximal dissections who have significant comorbid
diseases that preclude urgent surgery ought to be
treated medically. The goals of medical treatment in
patients with acute aortic dissections are to stabilize
the dissection, prevent rupture, accelerate healing,
and reduce the risk of complications.147
The potential problems encountered during medical treatment could be the extension of the dissection, expansion of the aneurysm, and compression of
the adjacent structures, resulting in organ malperfusion. The clinical picture of these patients includes
recurrent episodes of pain, abdominal distension,
increasing metabolic acidosis, progressive elevation
of liver enzymes, and/or worsening of renal function.
Serious consideration should be given to performing
surgery in these patients. The main causes of death
in patients being treated medically are aortic rupture
and organ malperfusion.
Surgical Treatment
Surgical intervention is indicated in all patients
with proximal dissections, with the exception of
patients with serious concomitant conditions that
preclude surgery.148 Stroke is often a contraindication to surgery because there is real concern that
anticoagulation therapy and reperfusion can result in
further neurologic deterioration by converting the
ischemic stroke to a hemorrhagic stroke. A careful
assessment for the presence of aortic regurgitation
and pericardial effusion, the extension of the dissection into the major aortic branches, the localization
of entry and reentry sites, and the presence of
thrombosis in the false lumen yields information that
can be helpful in planning the approach to and the
extent of surgery.149 The indications for performing
early surgery in patients with distal dissections are
the rapid expansion of a dissecting aneurysm, blood
leakage, impending rupture, persistent and uncontrollable pain, and/or impairment of the blood flow
to an organ or limb.150 –153 The operative mortality
rate for patients with aortic dissections ranges from
5 to 10% and may approach 70% in cases with
complications. The independent predictors of operative mortality include the presence of cardiac tamponade, the site of the tear, the time to operation,
the presence of renal/visceral ischemia, renal dysfunction, and the presence of pulmonary disease.154
The best technique for the surgical treatment of
322
aortic dissection has yet to be determined. The
best-known procedures for complete replacement of
the ascending aorta are the Bentall, the Cabrol, the
button, and the elephant trunk techniques.8 The
selection of a particular surgical technique has to be
determined by each surgeon in the light of his own
experience. Most of the surgical procedures are
combined with glue aortoplasty.155 The aim of surgical treatment is to excise and replace the aortic
segment containing the origin of the dissection, not
to replace the entire dissected aorta. In about 50% of
patients who are treated surgically, a part of the
aortic dissection persists.
Glue aortoplasty is an important contribution to
modern-day aortic dissection surgery. Tissue adhesives are used to conjoin the dissected aortic
wall layers and to aid the performance of bloodtight anastomosis on the aorta. The first tissue
adhesive, which was used in the 1970s, was gelatinresorcin-formalin glue.156 With the use of glues, a
complete disappearance of the false lumen has
been achieved in Пѕ 50% of the patients.157,158 The
use of tissue glue has been reported to significantly reduce the number of aortic valve replacements, the amount of intraoperative and postoperative bleeding, the volume of intraoperative
blood transfusions, and the frequency and severity
of postoperative complications.159 –161 Although
better long-term postoperative survival rates have
been reported since the start of the use of glue
aortoplasty in the 1970s, no controlled studies
have directly compared the effect of glue aortoplasty on long-term postoperative survival.159 –161
Treatment With Endovascular Stent Placement
Interest has grown in treating patients with aortic
dissections with endovascular stent placement. So
far, studies on this technique have been conducted
in a small number of high-risk surgical patients,
mostly with descending aortic dissections who displayed symptoms of abdominal organ malperfusion
(ie, bowel, liver, and/or kidney) or lower extremity
malperfusion.162–168 The stents have been placed in
the true lumen or the false lumen and have been
combined with balloon fenestration of the intimal
flaps in some cases.162,163,167 Organ malperfusion and
ischemia in patients with aortic dissections are
caused by encroachment on the aortic lumen that
provides the blood supply to a branch vessel. The
lumen supplying blood to the branch vessel may be
the true lumen or the false lumen. A stent is
deployed through the percutaneous approach within
the lumen supplying the branch vessel to hold the
lumen open by displacing the intimal flap toward and
overcoming the pressure from the other lumen. To
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overcome the high pressures in the other lumen, a
balloon fenestration procedure may be combined
with the stent procedure. The fenestration alone has
been used to equalize the pressure between false and
true lumens to relieve the compression exerted by
the high-pressure lumen on the surrounding structures. A potential risk of fenestration is in allowing
distal embolization in the setting of partial thrombosis of the lumen.
The clinical success of endovascular stent placement for aortic dissection ranges from 76 to 100%
with a reported 30-day mortality rate of up to
25%.162–167 Data on the long-term follow-up of these
patients are scarce. According to a report by Slonim
et al162 on 40 patients with aortic dissections (distal
dissection, 30 patients; proximal dissection, 10 patients) who were treated with endovascular stent
placement, 10 patients died during the first month
and 5 more patients died during a subsequent mean
follow-up period of 29 months. The procedurerelated complications reported with aortic endovascular stent placement include bowel infarction, renal
failure, lower extremity embolism, false lumen rupture, and postimplantation syndrome (ie, transient
elevation of body temperature and C-reactive protein level, and mild leukocytosis), with the reported
incidence of these complications ranging from 0 to
75%.162–168
While the exact definition of the aortic dissection patients who will potentially benefit from
endovascular stent placement needs to be determined, at this time the procedure could be considered as a palliative measure for symptomatic
patients with distal aortic dissections whose symptoms are secondary to organ or lower extremity
malperfusion. The fenestration/stent treatment
could be used in those patients with proximal
dissections who are unstable for surgery that could
be performed later once they become stable.
Although smaller studies have reported early success with endovascular stent placement and a
trend for lower mortality rates, the true assessment of the effectiveness and safety of this procedure await the conducting of large-scale studies
with long-term follow-up. At present, about 13%
of patients with aortic dissections receive stentgraft treatment, and this proportion is steadily
increasing. With more data available and more
advancement in operator expertise, stent graft
placement may, in the future, become the standard treatment for most cases of distal aortic
dissection, because waiting for the complications
to occur may not be prudent since the operative
mortality rate in these situations approaches
70%.154
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Treatment of Aortic Intramural Hematoma and
Atherosclerotic Aortic Ulcer
The treatment of patients with both aortic intramural hematomas and atherosclerotic aortic ulcers is
similar to that for patients with classic aortic dissections and, likewise, depends on the aortic site involved. Both aortic intramural hematoma and atherosclerotic aortic ulcer are far more common in the
descending aorta and, therefore, are treated with
aggressive medical therapy. Medical therapy should
consist of the optimal control of BP, a decrease in
aortic pulse dP/dt, and the control of risk factors for
atherosclerosis, as well as close long-term follow-up.
Surgery is preferred for the treatment of patients
with intramural hematomas and atherosclerotic aortic ulcers in the ascending aorta and aortic arch, and
of patients with progressive dilatation and aneurysm
formation of the aorta, irrespective of the site of
involvement.32–36 In a meta-analysis of 143 patients
with aortic intramural hematomas, of whom 30
patients (21%) died, 20 deaths (67%) were due to
aortic dissection or rupture.169
Long-term Treatment and Follow-up
Although the dissection of the aorta is an acute
event, in most cases an underlying chronic and
generalized disease of the media of the aortic wall
predispose the aorta to dissection, and this underlying pathology persists even in those cases in
which the surgical repair is radical. The potential
for aneurysm formation, progressive dissection,
and redissection of the remainder of the aorta
demands careful monitoring of long-term survivors.170 –172 The long-term management of the
survivors of aortic dissection consists of aggressive
medical management and a close follow-up with
clinical and imaging assessment of the aorta to
detect potential complications, which could be
corrected at the initial stages with reoperations.
An enlarging saccular aneurysm portends an impending aortic rupture and should be repaired
promptly. On long-term follow-up, saccular aneurysms have been reported173 to develop in as many
as 14 to 29% of patients with distal dissections.
The long-term medical management consists of
optimal BP control and long-term therapy with
вђ¤-blockers, even in patients with no history of
hypertension. Patients with the hypertensive etiology of dissection have a better long-term survival
rate and are at lower risk of developing dissectionrelated long-term complications. A good control of
BP may reduce the incidence of redissection to
about one third of patients (ie, 45 to 17%).10
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323
Prognosis
Despite improved diagnostic and therapeutic
techniques, the overall in-hospital mortality rate of
patients with aortic dissections (ie, approximately
30% for patients with proximal dissections and approximately 10% for those with distal dissections) has
not decreased in the last 3 decades.174,175 The predictors of in-hospital mortality include proximal
dissection, age Пѕ 65 years, migrating characteristic
of the pain, shock, pulse deficits, and the presence of
neurologic deficits. The long-term survival rates of
patients with proximal aortic dissections who undergo surgical repair and survive long enough to
leave the hospital are 65 to 80% at 5 years and 40 to
50% at 10 years.147,174,176 Information on the longterm prognosis of patients distal aortic dissections
who have been operated on and of those who have
not been operated on is limited.176,177 The long-term
prognosis may vary within the group of patients with
distal aortic dissections, and outcome appears to be
particularly worse for patients with retrograde arch
and ascending aortic involvement and in those with
patent false lumens that are absent of thrombosis.147,150,177 The most common cause of death in
long-term survivors of aortic dissections is the rupture of the aorta due to a subsequent dissection or
aneurysm formation. The prognosis for patients with
aortic intramural hematomas is similar to that for
patients with classic aortic dissections.178
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